Some trailing Tree refactor changes

Author: dwijnand

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -16,9 +16,6 @@ import scala.annotation.tailrec
 
 trait TreeInfo[T <: Untyped] { self: Trees.Instance[T] =>
 
-  // Note: the <: Type constraint looks necessary (and is needed to make the file compile in dotc).
-  // But Scalac accepts the program happily without it. Need to find out why.
-
   def unsplice(tree: Trees.Tree[T]): Trees.Tree[T] = tree
 
   def isDeclarationOrTypeDef(tree: Tree): Boolean = unsplice(tree) match {

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -804,7 +804,7 @@ object Trees {
   }
 
   /** mods val name: tpt = rhs */
-  case class ValDef[+T <: Untyped] private[ast] (name: TermName, tpt: Tree[T], private var preRhs: LazyTree[T @uncheckedVariance])(implicit @constructorOnly src: SourceFile)
+  case class ValDef[+T <: Untyped] private[ast] (name: TermName, tpt: Tree[T], private var preRhs: LazyTree[T])(implicit @constructorOnly src: SourceFile)
     extends ValOrDefDef[T], ValOrTypeDef[T] {
     type ThisTree[+T <: Untyped] = ValDef[T]
     assert(isEmpty || (tpt ne genericEmptyTree))
@@ -814,7 +814,7 @@ object Trees {
 
   /** mods def name[tparams](vparams_1)...(vparams_n): tpt = rhs */
   case class DefDef[+T <: Untyped] private[ast] (name: TermName,
-      paramss: List[ParamClause[T]], tpt: Tree[T], private var preRhs: LazyTree[T @uncheckedVariance])(implicit @constructorOnly src: SourceFile)
+      paramss: List[ParamClause[T]], tpt: Tree[T], private var preRhs: LazyTree[T])(implicit @constructorOnly src: SourceFile)
     extends ValOrDefDef[T] {
     type ThisTree[+T <: Untyped] = DefDef[T]
     assert(tpt ne genericEmptyTree)
@@ -855,7 +855,7 @@ object Trees {
    *                            if this is of class untpd.DerivingTemplate.
    *                            Typed templates only have parents.
    */
-  case class Template[+T <: Untyped] private[ast] (constr: DefDef[T], parentsOrDerived: List[Tree[T]], self: ValDef[T], private var preBody: LazyTreeList[T @uncheckedVariance])(implicit @constructorOnly src: SourceFile)
+  case class Template[+T <: Untyped] private[ast] (constr: DefDef[T], parentsOrDerived: List[Tree[T]], self: ValDef[T], private var preBody: LazyTreeList[T])(implicit @constructorOnly src: SourceFile)
     extends DefTree[T] with WithLazyField[List[Tree[T]]] {
     type ThisTree[+T <: Untyped] = Template[T]
     def unforcedBody: LazyTreeList[T] = unforced
@@ -924,12 +924,12 @@ object Trees {
     myTpe = NoType.asInstanceOf[T]
     type ThisTree[+T <: Untyped] = Thicket[T]
 
-    def mapElems(op: Tree[T] => Tree[T] @uncheckedVariance): Thicket[T] = {
+    def mapElems[U >: T <: Untyped](op: Tree[T] => Tree[U]): Thicket[U] = {
       val newTrees = trees.mapConserve(op)
       if (trees eq newTrees)
         this
       else
-        Thicket[T](newTrees)(source).asInstanceOf[this.type]
+        Thicket[U](newTrees)(source).asInstanceOf[this.type]
     }
 
     override def foreachInThicket(op: Tree[T] => Unit): Unit =

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -156,9 +156,9 @@ object Contexts {
     final def owner: Symbol = _owner
 
     /** The current tree */
-    private var _tree: Tree[? <: Untyped]= _
-    protected def tree_=(tree: Tree[? <: Untyped]): Unit = _tree = tree
-    final def tree: Tree[? <: Untyped] = _tree
+    private var _tree: Tree[?]= _
+    protected def tree_=(tree: Tree[?]): Unit = _tree = tree
+    final def tree: Tree[?] = _tree
 
     /** The current scope */
     private var _scope: Scope = _
@@ -469,7 +469,7 @@ object Contexts {
     }
 
     /** The context of expression `expr` seen as a member of a statement sequence */
-    def exprContext(stat: Tree[? <: Untyped], exprOwner: Symbol): Context =
+    def exprContext(stat: Tree[?], exprOwner: Symbol): Context =
       if (exprOwner == this.owner) this
       else if (untpd.isSuperConstrCall(stat) && this.owner.isClass) superCallContext
       else fresh.setOwner(exprOwner)
@@ -592,7 +592,7 @@ object Contexts {
       assert(owner != NoSymbol)
       this.owner = owner
       this
-    def setTree(tree: Tree[? <: Untyped]): this.type =
+    def setTree(tree: Tree[?]): this.type =
       util.Stats.record("Context.setTree")
       this.tree = tree
       this

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -40,7 +40,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
 
   override def printerContext: Context = myCtx
 
-  def withEnclosingDef(enclDef: Tree[? <: Untyped])(op: => Text): Text = {
+  def withEnclosingDef(enclDef: Tree[?])(op: => Text): Text = {
     val savedCtx = myCtx
     if (enclDef.hasType && enclDef.symbol.exists)
       myCtx = ctx.withOwner(enclDef.symbol)
@@ -990,7 +990,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   }
 
   protected def toTextPackageId[T <: Untyped](pid: Tree[T]): Text =
-    if (homogenizedView && pid.hasType) toTextLocal(pid.tpe.asInstanceOf[Showable])
+    if (homogenizedView && pid.hasType) toTextLocal(pid.typeOpt)
     else toTextLocal(pid)
 
   protected def packageDefText(tree: PackageDef): Text = {

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -1390,7 +1390,7 @@ import cc.CaptureSet.IdentityCaptRefMap
            |""".stripMargin
   }
 
-  class TypeDoesNotTakeParameters(tpe: Type, params: List[Trees.Tree[Trees.Untyped]])(using Context)
+  class TypeDoesNotTakeParameters(tpe: Type, params: List[untpd.Tree])(using Context)
     extends TypeMsg(TypeDoesNotTakeParametersID) {
     private def fboundsAddendum =
       if tpe.typeSymbol.isAllOf(Provisional | TypeParam) then